Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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530 FXUS62 KRAH 221527 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1025 AM EST Mon Jan 22 2018 .SYNOPSIS...
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A cold front will approach from the west today, and cross central NC Tuesday morning. High pressure and associated seasonably cool and dry conditions will follow for mid-week.
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&& .NEAR TERM /THROUGH THIS EVENING/...
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As of 1025 AM Monday... Just minor tweaks made to the near term forecast, mainly around timing of scattered showers later this evening. 12Z upper air analysis along with satellite imagery depict a deep and mature cyclone over the central Plains. This system projected to lift newd as strongest winds aloft have rounded the base of the upper level trough. While the atmosphere over central NC remains relatively dry, flow above 400mb advecting enough moisture to produce a veil of high clouds overhead. This deck of high clouds currently thick enough to inhibit sunshine across the Piedmont, though looking upstream, some thin spots noted. Thus, some potential for at least partly sunny skies this afternoon. This warmth along with a steady sly low level flow should allow temperatures to recover into the 60s this afternoon. The aforementioned sly flow will advect enough moisture to support the formation of stratocu deck late this afternoon, mainly south of highway 64. As the atmosphere continues to moisten, could see an isolated shower or two streak nwd across the region after 4 PM. Latest near term model guidance has slowed the arrival of the better lift of showers until 06Z or later. So have delayed the timing of higher pops a few hours across the western Piedmont this evening.
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&& .SHORT TERM /TONIGHT AND TUESDAY/...
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As of 400 AM Monday... Tonight: A warm front and associated leading edge of surface dewpoints in the 50s will surge nwd across cntl NC tonight, with low temperatures likely to occur during the mid-evening hours, before slowly rising overnight. Despite the increasing surface theta-e, bufr forecast soundings suggest a shallow, near-surface stable layer will likely remain in place, thereby muting surface-based instability and threat of severe weather overnight. Nonetheless, HREF mean MUCAPE values are forecast to climb to around 250 J/kg between 06-12Z, in a strong WAA regime driven by a 45-60 kt sswly llj at 925-850 mb. As such, scattered to numerous (slightly elevated) showers are apt to develop and overspread cntl NC, along the axis of the llj, overnight. Tuesday: The warm front will be quickly followed by an effective (lead) cold front forecast to cross cntl NC between 12-15Z over the nw Piedmont and between 18-20Z over the Coastal Plain. The passage of this cold front --one that may be better characterized as a dry line, and accompanying broken line of convection-- will result in clearing, drying the in the low levels, and the deepening of a diurnal mixed layer that will promote the development of strong sswly winds and associated gusts that will peak in the 30s kts per bufr forecast soundings. In addition, some realization of weak surface-based instability may occur ahead of the convective line with diurnal heating, mainly east of Hwy 1, though widespread pre-frontal cloudiness will limit this heating and associated destabilization, to a several hundred J/kg or less. Nonetheless, a few strong convective wind gusts will be possible as the line moves east. Any appreciable cooling will lag this feature and not occur until a secondary front settles sewd across cntl NC after 21Z. High temperatures will consequently again climb into the 60s, to lwr 70s over the sern CWFA. Storm total precipitation amounts are expected to be around a tenth to quarter inch on average, and scattered, so a widespread soaking rain is not anticipated.
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&& .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... As of 210 AM Monday... Expect dry weather through Friday night. An upper level shortwave and a reinforcing dry cold frontal passage is expected Wednesday night/Thursday. Surface high pressure is expected to build into the area in the wake of the secondary cold front and remain over the area into Saturday. The upper level ridge will move eastward over the Carolinas through Friday night. Another upper level trough and surface cold front will develop over the Midwest and progress eastward toward the Mid-Atlantic over the weekend. As southwesterly flow increases, so will the warm, moist advection into the region. As a result, cloud cover and chances for precipitation will increase late Saturday into Sunday as the cold front approaches. As of the latest forecast cycle, the front progresses through Central NC by Sunday night, with cool high pressure building in behind it. Highs will be generally in the upper 40s north to mid 50s south through Friday and lows in the upper 20s to low 30s Wednesday and Thursday nights. Temperatures will moderate through Sunday, cooling down once again in the wake of the front. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... As of 720 AM Monday... The flow around high pressure off the NC coast will allow a warm front and associated leading edge of more humid/moist air to surge into cntl NC from south to north between 22Z-06Z. A lead band of 2500-4000 ft stratocumulus will accompany the warm front; and this may result in an MVFR ceiling and a widely scattered shower around FAY as early as 22Z. Sly flow will strengthen, particularly just above a shallow layer of stability near the surface, to around 40-45 kts at 1500 ft late this evening-early tonight; and this will result in both the newd development of widespread 500-1200 ft ceilings and low level wind shear conditions between 02Z-07Z. Initially scattered showers will also become more numerous overnight, with a few thunderstorms possible Tue morning. Outlook: The above-referenced IFR-MVFR and llws conditions, and showers and isolated thunderstorms, will persist until a cold front crosses cntl NC from west to east on Tue. A subsequent return to VFR will result behind the cold front, generally between 12Z-15Z at Triad sites and around 18-20Z at ern ones. A very breezy swly wind will also develop behind the front, with gusts to around 35 kts probable for at least a few hours on Tue. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...WSS NEAR TERM...WSS SHORT TERM...MWS LONG TERM...KC AVIATION...MWS

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